disulphide and the solution gently shaken with a smaU drop of cone, sul-
phuric acid : a fine purple-violet coloration, rapidly changing to brownish-
red, is obtained.
Other marine animal oils, treated similarly, give no violet coloration
(see preceding article).
2. Acid Number .—As in General Methods, 7.
3. Test for Added Iodine (Inorganic) .—About 10 c.c. of oil are
shaken with as much water, the latter being then separated and treated
with starch paste and either cone, nitric acid or chlorine water: appear-
ance of a blue coloration indicates inorganic iodine.
4. Freezing Point.—The oil is maintained at o° for some time to
ascertain if it remains liquid.
5. Detection of Adulterations.—The oil may contain the following
(a) OTHER FISH-LIVER OILS. No certain methods are known of dis-
tinguishing different fish-liver oils or their mixtures.
I (&) FISH AND BLUBBER OILS. No certain method exists of detecting
fish-oil in cod-liver oil. Addition of blubber oil (whale, seal) may be sus-
pected as a result of determinations of the iodine number, the Maurnene
number and the refractometer reading (Zeiss), which are lowered by whale
or seal oil (see Table XLVIII).
(c) VEGETABLE AND MINERAL OILS. These are recognised by the
methods given in the preceding article (Fish and Blubber Oils).
According to the Official Italian Pharmacopoeia, medicinal cod-liver oil is
amber or straw-yellow, D at 15° =0-922-0-930, iodine number = 150-170.
When cooled to o° it does not congeal, but deposits flocks of white solid matter.
It should give the reaction for fish-liver oils and should contain no inorganic
iodine (test 3).
The acidity is low in white oils, especially in so-called steam liver oil (o -3-
2% as oleic acid), but is higher (up to 8%) in the more highly coloured yellow
or pale oil and may reach about 30% in brown oils.
Waxes are composed "essentially of compounds of certain fatty acids
(palmitic, stearic, cerotic) with higher alcohols (cetyl, myricyl alcohols) ;
some contain also a certain amount of free acids (beeswax, carnauba wax)
and solid hydrocarbons (beeswax). Waxes are of animal origin, such as
beeswax, Chinese insect wax, wool fat and spermaceti, and of vegetable
origin, such as carnauba wax, fig wax, ocuba wax, etc. The latter should
not be confused with other vegetable products known as waxes, these being
really fats, such as Japan wax and myrtle wax (see Vegetable Fats).
The waxes of greatest importance are: beeswax, wool fat, spermaceti
and the,;corresponding oil, which are dealt with in detail. Of the other
waxes the characters are given in Table XLIX.
A.C. 280 1 24-33 ! 66